The present invention relates to a recording/reproducing apparatus for recording and reproducing picture and sound data, and more particularly, to an optimum recording/reproducing apparatus capable of optimally performing the recording and reproducing of the data while taking into account and adapting to changes in the recording and reproducing environments.
In general, when recording and reproducing picture and sound data, the data are recorded in digital form onto a recording medium such as magnetic tape or a magnetic disk, and thus recorded, are reproduced so as to restore the original image and sound. In recording and reproducing the image and sound data via a predetermined recording medium, there have been continued attempts to increase the quantity of data which can be stored on a medium of limited size, as well as to secure better picture and sound qualities without degradation thereof.
The conventional digital recording/reproduction apparatus is designed to record and reproduce the data while basically fixing the recording rate, error correction capability, and compression ratio at constant values. This, however, prevents the achievement of optimum recording and reproduction since picture and sound quality are easily influenced by the recording medium's characteristics, set apparatus capability, etc.
Moreover, even if a high-quality head (the most important component of a data recording and reproducing apparatus) is well-manufactured, the same type of tape is used for each recording, and each apparatus is manufactured by the same method through the identical production line, thousands or tens of thousands of viewing and listening devices used by the consumer would not have the same capability. Therefore, even if the same picture and sound data are recorded or reproduced, the same sound or picture quality cannot be obtained in use. Accordingly, the choice of recording tape and viewing/listening apparatus may cause differences and degradation in picture and sound quality.
The above-described problems will be explained with reference to FIGS. 1 through 5, which show actual experimental data.
FIG. 1 illustrates the relationship between the distance (gap) between the head of the set apparatus and the recording medium, i.e., the tape, and the reproduced output. Referring to FIG. 1, as the distance between head and tape decreases, the reproduced output increases. Thus, it should be noted that even if all set apparatus are made as identically as possible, minute changes in the distance between head and tape produce differences in reproduced output.
FIG. 2 shows the relationship between tape type and reproduced output. Referring to FIG. 2, tape NEW ME, which has composition of Hc=1680(0e) and Br=4050(0e), exhibits the best characteristics of the types shown. Accordingly, it should be noted that when recording/reproduction is performed by a given apparatus, reproduction output differs according to the composition of the tape on which the data are recorded.
FIG. 3 shows the relationship between thickness of the body of the magnetic tape and reproduction loss. In FIG. 3, the difference of reproduction loss is shown for thicknesses of 0.20 .mu.m and 0.25 .mu.m, with less reproduction loss being attained when the body of the magnetic tape is 0.20 .mu.m thick. Thus, a thinner tape dimension reduces reproduction loss.
FIGS. 4A, 4B and 4C show the relationship between recording current and reproduction characteristic. Here, it is noted that for the same recording signal, even small changes in recording current produce different reproduction characteristics.
FIGS. 5A, 5B and 5C show the relationship between the recording bit rate and the reproduction characteristic. A lower recording bit rate results in better reproduction characteristics. The characteristics are variable according to the kind of tape, the head's capability, and the performance of recording current.
The operation of a conventional digital signal recording/reproducing apparatus (made without taking into consideration the specific characteristics of the tape, head, set apparatus, etc.) will be briefly described with reference to FIGS. 6 and 7.
FIG. 6 is a block diagram illustrating the conventional digital recording apparatus. Referring to FIG. 6, reference numeral 10 denotes an analog-to-digital (A/D) converter for converting an analog signal into digital form, 15 denotes an error correction encoder for error-correction, 20 denotes a modulator for modulating the data to be adapted for the channel characteristic, and 25 denotes an amplifier for amplifying the data signal to the proper amplitude for being recorded onto the recording medium. Audio data are in analog form and are therefore converted into the form of a digital signal via A/D converter 10. The converted data are input to error correction encoder 15 (in general, a Reed Solomon (RS) coder is used) for detecting and correcting errors. The error-corrected data are modulated by modulator 20 to be suitable for the channel characteristic thereof. That is, if the digital data are communication data, the data are frequency modulated into a communication frequency band. When the data are to be recorded on a recording medium, e.g., magnetic tape, the data are modulated into a frequency band suitable for recording. Having been modulated adaptively for a specific channel's characteristics, the digital data are then amplified to the proper amplitude by amplifier 25, so as to be recorded on the recording medium.
FIG. 7 is a schematic block diagram showing the conventional digital reproducing apparatus. Referring to FIG. 7, reference numeral 25 denotes an amplifier for performing the same function as that of FIG. 6, 30 denotes a demodulator for performing the inverse procedure of the modulation performed in the above recording process, 35 denotes a decoder for decoding the input data, and 40 denotes a digital-to-analog (D/A) converter for converting a digital signal into an analog signal. The digital signal reproducing apparatus as shown in FIG. 7 reproduces the picture or sound digital data from the recording medium, using the reproducing head shown in FIG. 8, then receives the reproduced data via amplifier 25, to thereby amplify the data up to a predetermined amplitude. The thus-amplified signal enters demodulator 30 and undergoes a demodulation process which is the inverse of that performed during recording, to be demodulated. The thus-demodulated data are error-detected and error-corrected by error correction decoder 35 (a Viterbi decoder or RS decoder can be used). The error-corrected picture or sound digital data are converted into analog form by D/A converter 40, and are then transmitted to a display device and speaker or the like, for output as a picture with sound.
The conventional digital recording/reproducing apparatus shown in FIGS. 6 and 7 performs the recording and reproduction of data after fixing the data recording rate and track length, and therefore picture and sound quality are degraded according to differences in the recording medium's characteristics and variations in the system's capability.
Also, as most electrical and electronic products are mass-produced, even the consistent use of a particular head type, recording medium (i.e., tape), and recording/reproducing apparatus cannot guarantee consistent recording and reproduction quality. That is, a user may employ tapes manufactured with various substances, such that data cannot be recorded on the recording medium at the optimum condition and the recorded data cannot be reproduced under optimum conditions. Accordingly, the sound and picture quality are unavoidably degraded.